But it is the president, not the generals and admirals, who have made this unthinkable situation part of the new normal in the Age of Trump. No modern president has been so reckless in his criticism of both active and retired military professionals. When Trump said he knows more than the generals—a laughable claim from almost any civilian when it comes to military affairs—he apparently meant it. And that means he has no respect for military advice, from any direction. This, more than any personal clash, was the clear message in Mattis’s resignation.

If Trump continues on this path—and he will—we could face the most politicized and divided military since Vietnam, or even since the Civil War. Generals and admirals could be faced with betraying their professional code either by giving the advice they know will keep them in the good graces of the president, or by ignoring the president’s orders and protecting their troops in the field as they think best. The rank and file, meanwhile, will become accustomed to showing up at political rallies where their commander in chief will pander to them and air his grievances against other elected officials, all while they wave banners in uniform and cheer for a growing cult of personality.